Point-of-care ultrasound may elucidate reversible causes of cardiac arrest, and its use is supported by international guidelines in the periarrest setting. We present a case in which the treatment of cardiac arrest caused tension pneumothoraces and cardiac tamponade by pneumopericardium. Both pneumothorax and tamponade were expected to be identified with ultrasound, but were not. Subcutaneous emphysema precluded the diagnosis of pneumothorax. Cardiac imaging was false negative for tamponade, because the latter was caused by air and not fluid. Diagnoses are not to be excluded with inconclusive point-of-care ultrasound examinations, which should prompt further clinical evaluation and imaging.